WO2008138742A1

WO2008138742A1 - Injector having a pressure-compensated control valve

Info

Publication number: WO2008138742A1
Application number: PCT/EP2008/055204
Authority: WO
Inventors: Thomas Pauer; Andreas Rettich
Original assignee: Robert Bosch Gmbh
Priority date: 2007-05-14
Filing date: 2008-04-29
Publication date: 2008-11-20
Also published as: EP2156044A1; DE102007022587A1; EP2156044B1

Abstract

The invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine, particularly a common rail injector, comprising a valve element (2), which can be switched from a closed position to an open position in which it releases the fuel flow into the combustion chamber, and a control valve (10) that is at least approximately pressure-compensated in the axial direction, having an actuating element (12) adjustable on a valve seat (16). According to the invention, a sealing diameter of the actuating element resting against the valve seat is less than 3 mm.

Description

description

title

Injector with pressure compensated control valve

State of the art

The invention relates to an injector for injecting fuel in a combustion chamber of an internal combustion engine, in particular a common rail injector according to the preamble of claim 1.

Injectors with a pressure-balanced in the axial direction control valve (servo valve) are known in two fundamentally different designs. Due to the pressure balance of the control valve, such injectors are particularly suitable for switching high fuel pressures, in particular beyond 2000 bar.

In the case of the injector design known from EP 1 612 403 A1, the actuator of the control valve is designed as a valve sleeve. The valve sleeve defines a valve chamber formed on a diameter-reduced portion of a guide pin only radially outward, so that act from the inside of the valve chamber located under high pressure fuel no forces in the axial direction on the valve sleeve. In addition, injectors are known in which the valve sleeve of the control valve is guided not on its inner circumference, but on its outer periphery. In one variant of these injectors, only a pressure pin which is pressurized in the axial direction is arranged inside the valve sleeve, which pushes the valve chamber provided inside the valve sleeve in an axial upward direction. seals. In this variant too, the high-pressure fuel within the valve chamber does not act on the valve sleeve in the axial direction. In another variant of the control valve with valve sleeve, the valve chamber is arranged radially outside the valve sleeve. When lifted from the valve seat valve sleeve, the valve chamber is connected via a channel formed by the valve sleeve with the low pressure region of the injector.

In a second injector design, the actuator is designed as a valve pin, wherein a valve chamber of the control valve is provided at a reduced diameter portion of the valve pin. This design of axially balanced control valves is characterized in that the effective in two opposite axial directions, the valve chamber limiting pressure application surfaces on the valve pin are the same size, so that the forces acting in the opposite axial directions compressive forces cancel each other.

All injectors with pressure-balanced control valves, regardless of their concrete design common, that the sealing diameter of the actuator, ie the valve chamber immediately limiting, applied to the valve seat diameter of the actuator increases over the life of the injector due to wear and tear. This creates a pressure acting in the opening direction, which causes the injectors are only approximately equal to pressure. As a result, the opening and closing behavior of the control valve changes greatly over its lifetime. DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose an injector, in which the wear effects on the opening and closing behavior are minimized.

Technical solution

This object is achieved with the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features specified in the description, the claims and / or the figures also fall within the scope of the invention. For specified value ranges, values lying in the value ranges should also be disclosed as limit values and can be used as desired.

The invention is based on the idea that the sealing diameter of the actuator is less than 3 mm, at least immediately after production, ie before the use of the injector. Under sealing diameter in the context of the invention is understood to mean the valve seat fitting, the valve chamber directly limiting diameter of the actuator. Preferably, the sealing diameter is chosen so that the sealing diameter does not exceed 3 mm also due to wear during operation of the injector. The provision of a sealing diameter of less than 3 mm has the advantage that the surface of a pressure stage which arises during operation is comparatively small, and consequently also the compressive force acting on the actuator in the opening direction. This is due in particular to the fact that the area of the resulting printing increases quadratically with increasing sealing diameter. The effects of (inevitable) wear on the opening and closing behavior of the control valve and thus on the opening and closing behavior of the valve element are thus comparatively low due to the small sealing diameter. The increasing pressure forces over time are therefore moderate and therefore manageable. Another advantage of choosing a small sealing diameter of less than 3 mm is the resulting low weight of the actuator to be adjusted axially, so that actuators with low power and thus with low space requirements can be used. Likewise, acting on the actuator closing spring can be dimensioned much smaller, which in turn has a positive effect on the required space. The lower mass of the actuator leads at the same time in turn to less wear of the actuator and / or the valve seat.

Under pressure-balanced control valves in the axial direction are understood in the sine of the invention also control valves, in which already in the production of a minimum pressure level, i. a one-sided pressure application surface is provided, for example in order to counteract a diameter step that arises as a result of wear, or to specifically generate a low opening force, in particular in order to be able to use actuators with lower power.

In an embodiment of the invention is advantageously provided that the sealing diameter, ie the valve chamber on the valve seat directly limiting diameter of the actuator is selected from a range between 2.5 mm and 2.95 mm. Even more advantageous is the sealing diameter from a diameter range between about 1.5 mm and about 2.0 mm. Of particular advantage is an embodiment in which the sealing diameter is selected from a diameter range between about 1.0 mm and about 1.5 mm. Particularly advantageous effects on minimized wear have a sealing diameter ranging between about 0.5 mm and about 1.0 mm.

Of particular advantage is an embodiment in which the axially spaced from the sealing diameter, the valve chamber on the opposite axial side limiting diameter of the actuator is also smaller than 3.0 mm. This diameter is either a guide diameter of the actuator, such as in an embodiment in which the actuator is formed as a valve sleeve and is guided on a radially inner guide pin, or in an embodiment in which the actuator is guided as in a valve piece Valve pin is executed. In a construction variant of the control valve with a valve sleeve guided on the outer circumference and a pressure pin arranged inside the valve sleeve, this is a second sealing diameter in the axial direction of the sealing diameter resting against the valve seat, with which the valve sleeve is on the lower side at the lower side of the pressure pin is applied.

Preferably, the guide diameter or the second sealing diameter of the actuator is selected from a range between about 2.5 mm and about 2.95 mm. Particularly preferred is an embodiment in which the guide diameter or the second sealing diameter is selected from a range between about 2.0 mm and about 2.5 mm. Particularly advantageous is an embodiment with a guide diameter or a second sealing diameter from a range between about 1.0 mm and about 1.5 mm. A particularly preferred embodiment is formed with a guide diameter or a second sealing diameter from a range between about 0.5 mm to about 1.0 mm.

It is particularly advantageous if the sealing diameter of the actuator resting against the valve seat (at least immediately after production) is the same as that of the axially spaced guide diameter or the same as the second sealing diameter spaced in the axial direction.

This ensures that the control valve is, at least immediately after production, a control valve which is completely pressure-balanced in the axial direction.

The provision of a sealing diameter of less than 3 mm can be realized in a control valve in which the actuator is designed as a valve sleeve. In this case, the sealing diameter is the inner diameter of the valve sleeve, with which the valve sleeve rests against the valve seat, for example a conical seat. According to a first alternative, the valve sleeve is guided on its inner circumference on a guide pin, which is preferably formed integrally with a valve piece, which preferably carries the valve seat. In this variant, a valve chamber is delimited in the axial direction by the sealing diameter (inner diameter of the valve sleeve) resting against the valve seat and by a guide diameter which is spaced apart in the axial direction and with which the valve sleeve is connected to the guide sleeve. bolt is guided. The guide diameter preferably corresponds to the sealing diameter. The outer diameter of the guide pin corresponds approximately to the inner diameter of the valve sleeve minus a minimum guide clearance.

According to a second alternative, the valve sleeve is guided on its outer circumference. Preferably, in this embodiment, a pressure pin is located inside the valve sleeve, wherein the inner diameter of the valve sleeve bearing against the pressure pin is a second sealing diameter (not the guide diameter).

In a third alternative of an injector with an axially adjustable valve sleeve, the valve chamber is arranged on the outer circumference of the valve sleeve. In this variant, the sealing diameter of less than 3.0 mm is the outer diameter of the valve sleeve lying against the valve seat.

In addition, the invention can be realized in an injector with a control valve whose actuator is designed as a valve pin. In this embodiment, the sealing diameter preferably corresponds to the voltage applied to the valve seat outer diameter of the valve pin, which is preferably formed by a conical portion of the guide pin. Opposite in the axial direction, the valve chamber of such a control valve is limited by a guide diameter (outer diameter) of the valve pin.

Preferred is an embodiment in which the diameter of the valve pin within the valve chamber of the control valve is smaller, preferably by at least about 0.5 mm is smaller than the sealing diameter of the valve pin and thus also less than the guide sleeve diameter spaced apart in the axial direction of the valve pin.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. These show in:

1 shows a first possible embodiment of a control valve of an injector, in which the control valve has an actuator designed as a valve pin,

2 shows a second embodiment of a control valve for an injector, in which the actuator is designed as a guided on a guide pin valve sleeve,

3 shows a further embodiment of a control valve of an injector, in which the valve sleeve is guided on its outer circumference and

4 shows a further embodiment of a control valve with an axially adjustable valve sleeve, in which a valve chamber of the control valve is arranged on the outer circumference of the valve sleeve. Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1, a fragment designed as a common rail injector injector 1 for injecting fuel into a combustion chamber, not shown, of an internal combustion engine is shown. The injector 1 comprises an adjustable in the axial direction one or more parts valve element 2, which is adjustable between a closed position of the fuel flow from a nozzle hole arrangement not shown releasing opening position. The valve element 2 delimits with an upper end face 3 a control chamber 4 radially inside a sleeve 5. In the sleeve 5, an inlet throttle 6 is introduced, via which the control chamber 4 is permanently supplied with high-pressure fuel. The control chamber 4 is connected via an introduced into a valve piece 7 outlet throttle 8 with a valve chamber 9 of a control valve 10. With the control valve 10 open, fuel can flow from the control chamber 4 into a low-pressure region 11 of the injector and from there to an injector return not shown. The flow cross-sections of the outlet throttle and the inlet throttle 6 are matched to one another such that when the control valve 10 is open, a net outflow of fuel from the control chamber 4 results, whereby the closing forces acting on the valve element 2 decrease and thus the valve element 2 from its valve seat (not shown) lifts off and releases the fuel flow into the combustion chamber. If the control valve 10 is closed, flows through the inlet throttle 6 continue to fuel in the control chamber 4, so that the pressure in the control chamber 4 and thus increase the force acting on the valve element 2 axial closing forces, so that the injection process is interrupted.

The control valve 10 comprises an adjustable in the axial direction as a valve pin formed actuator 12, which is formed integrally with an anchor plate 13 in this embodiment. The armature plate 13 is part of an electromagnetic actuator, not shown, for opening the actuator 12. To close the bolt-shaped actuator 12, a closing spring 14 is provided.

The valve chamber 9 is partially formed within the valve member 7 and partially on a reduced diameter portion 15 of the actuator 12, wherein the pressure in opposite axial directions pressure application surfaces of the actuator 12 are equal.

At the top of the valve piece 7, a valve seat 16 is formed for engaging a conical portion 17 of the actuator 12. The actuator 12 is located with a sealing diameter D on the valve seat 16. In this embodiment, the sealing diameter D of about 2.5 mm is an outer diameter of the actuator 12 at its conical portion 17th

On the axial side opposite the sealing diameter D, the valve chamber 9 is delimited by a guide diameter D _{F of} the actuator 12. With the guide diameter D _F , the actuator 12 is radially on the outside of a guide bore 18 in the valve piece 7 at. The amount of the management diameter D _F corresponds to the amount of the sealing diameter D of the actuator 12th

Over the life of the injector 1 occurs wear in the region of the valve seat 16 and the conical portion 17 of the bolt-shaped actuator 12, so that the sealing diameter D increases. Due to the choice of a small sealing diameter D of 2.5 mm in this embodiment and the associated low weight of the valve pin 12, the wear is minimal. In addition, the resulting pressure application surface is also minimal due to the small sealing diameter D, so that the pressure forces acting in the opening direction are limited and therefore manageable.

As can be seen from FIG. 1, the lower end face 19 of the actuator 12 delimits a compensation chamber 20, which is connected to the low-pressure region 11 of the injector via a connecting channel 21, so that the pressure in the compensation chamber 20 during a displacement movement of the actuator 12 at least approximately constant.

FIG. 2 shows an alternative exemplary embodiment of an injector 1, the basic mode of operation of the injector shown corresponding to the mode of functioning of the injector 1 according to FIG. 1. In contrast to the embodiment of FIG. 1, the actuator 12 is not formed as a valve pin, but as an axially adjustable valve sleeve 12, which is integrally formed with an anchor plate 13. The actuator 12 is guided radially inwardly on an axially extending guide pin 22, which is integral with a valve piece 7 is formed, on which also the valve seat 16 of the control valve 10 is located.

The valve chamber 9 is formed on a reduced diameter portion 15 of the guide pin 22 and is supplied via an outlet throttle 8 with fuel from the control chamber 6. The sleeve-shaped actuator limits the control chamber 6 only radially on the outside and lies with a guide diameter D, which is formed by an inner diameter of the sleeve-shaped actuator 12 on the valve seat 16 at. The sealing diameter is in this embodiment about 2.3 mm.

On the Axialsei- the sealing diameter D opposite the valve chamber 9 is limited by a guide diameter D _F , which corresponds to the sealing diameter D.

The embodiment of FIG. 3 corresponds in its operation to the embodiments of FIGS. 1 and 2. In contrast to the embodiment of FIG. 2, the sleeve-shaped actuator 12 is guided on its outer circumference, wherein in the valve member 7, an axial channel 23 is formed through which fuel can flow in the low-pressure region 11 of the injector when the actuator 12 is lifted from the valve seat 16. Within the sleeve-shaped actuator 12 is a pressure pin 24 which is supported in the axial direction on a holding body 25 of an electromagnetic actuator. The sleeve-shaped actuator 12 bears against the valve seat 16 with a sealing diameter D formed by an inner diameter. The valve chamber 9 is bounded on the opposite axial side by a second sealing diameter D2. This is the inner diameter of the sleeve-shaped adjusting limb 12 edge side, with which the sleeve-shaped actuator 12 rests on the pressure pin 24 at the edge. In this embodiment, the sealing diameter D and the second sealing diameter D _{2 are} each 2.8 mm.

4, a further embodiment of an injector 1 is shown. Also in this injector 1, the basic operation corresponds to the injectors described in FIGS. 1 to 3. The actuator 12 is formed as a valve sleeve, wherein the valve seat 16 is formed on a valve member 7. The valve chamber 9 is arranged radially outside the valve sleeve 12, so that the sealing diameter D, with which the sleeve-shaped actuator 12 bears against its valve seat 16, is formed by an outer diameter of the actuator 12. The sealing diameter D is about 1.9 mm in this embodiment. Spaced in the axial direction of the sealing diameter D, the control chamber 9 is limited by a guide diameter D _{F of} the sleeve-shaped actuator 12. This is the outer diameter of the actuator 12, with which the actuator 12 rests against a peripheral wall of a guide bore 26 in a guide plate 27. With the control valve 10 open, that is lifted off from the valve seat 16 actuator 12 fuel flows from the control chamber 6 via the outlet throttle 8 and the valve chamber 9 centrally via the sleeve-shaped actuator 12 in the low pressure region 11 of the injector and from there to the Inj ektorrücklauf not shown ,

Claims

claims

1. injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular com mon Rail Inj ector, with an adjustable between a closed position and the fuel flow into the combustion chamber opening position openable valve element (2) and with a in the axial direction at least approximately pressure compensated control valve (10) with an actuator (12) which can be adjusted to a valve seat (16),

characterized,

in that a sealing diameter (D) of the actuator (12) resting against the valve seat (16) is smaller than 3 mm.

2. An injector according to claim 1, characterized in that the sealing diameter (D) from a range between about 2.5 mm and about 2.95 mm, preferably from a range between about 2.0 mm and about 2.5 mm, in particular from a range between about 1.5 mm and about 2.0 mm, more preferably from a range between about 1.0 mm and about 1.5 mm, in particular from a range between about 0.5 mm and about 1.0 mm is selected.

3. Injector according to one of claims 1 or 2, characterized in that a valve chamber (16) of the control valve (10) limiting, in the axial direction of the sealing diameter (D) spaced guide diameter (D _F ) or second sealing diameter (D ₂ ) of the actuator (12) is smaller than 3.0 mm.

4. An injector according to claim 3, characterized in that the guide diameter (D _F ) and the second sealing diameter (D ₂ ) from a range between about 2.5 mm and about 2.95 mm, preferably from a range between about 2, 0 mm and about 2.5 mm, in particular from a range between about 1.5 mm and about 2.0 mm, particularly preferably from a range between about 1.0 mm and about 1.5 mm, in particular from one area between about 0.5 mm and about 1.0 mm.

5. Injector according to one of claims 3 or 4, characterized in that the sealing diameter (D) is equal to the guide diameter (D _F ) or equal to the second sealing diameter (D ₂ ).

6. Injector according to one of the preceding claims, characterized in that the actuator (12) is designed as a valve sleeve.

7. Injector according to one of claims 1 to 5, characterized in that the valve sleeve is guided on its inner periphery on a guide pin (22).

8. An injector according to claim 6, characterized in that the valve sleeve is guided on its outer circumference.

9. Injector according to one of claims 1 to 6, characterized in that the actuator (12) is designed as a valve pin.

10. An injector according to claim 9, characterized in that the diameter of the valve pin is smaller within the valve chamber of the control valve, preferably smaller by at least 0.5 mm, than the sealing diameter of the valve pin.